Get the system to use the correct language with the "speak selection" feature

I'm trying to use OS X's native voice-recognition system to speak the highlighted text using the correct language. I enabled System Preferences > Accessibility > Spoken Content > Speak selection, keeping the default of Option + Esc. In some cases, the system will correctly identify the non-English words and will speak them with the correct accent, using a different voice (female; German): ich schreibe. In other cases, the system will not correctly identify the non-English words and will speak them with the default voice (male; English): ich spreche. Is there a way to tune this?